Dell Inspiron 15 long beep on startup - help!

Hi everyone.

I need help troubleshooting this issue:
I'm a novice, but I have enough technical knowledge to try fixing things myself.
Dell Inspiron 15, P T4500 processor, 3GB Random Access Memory, 320GB HDD
-Used by an elderly user (retiree)

-When powered on, it emits a continuous long beep. The screen stays black with the message 'press Formula 2 to enter setup'. Pressing Formula 2 does nothing, and the keyboard is completely unresponsive.

-Occasionally, if I tap the power button several times, Windows 7 starts loading. Once it boots, it runs perfectly fine. However, once it's shut down and restarted, the cycle repeats.

Sometimes I spend thirty minutes trying this; every single time it starts with that long beep... eventually, after rapid tapping of the power button, Windows might actually boot.

Naturally, holding the button down too long just forces a shutdown.
I initially suspected the battery since it's weak, but the behavior is identical when I remove the battery and run it directly off the AC adapter.

I thought it might be the Random Access Memory, but the sticks are functional and there's no dust buildup.

Could this be the CMOS battery? How would I verify that?

THANKS SO MUCH!!!

Grab the manual for the laptop or motherboard and figure out what that beep code actually means. That’s honestly the best advice anyone can give you. Once you know, go check the specific component it's flagging, along with the power supply and those power rails.

According to the folks at Dell, a single continuous beep usually points toward an issue with the Random Access Memory. How did you go about verifying that your memory sticks are actually working correctly?

I think your memory has officially gone to the great beyond
That constant, annoying beeping is such a clear sign that something's wrong with the Random Access Memory—either it’s completely fried, or it's well on its way to the afterlife.